In order to lose the required amount of weight for the present day scenes, Matt Damon went on a strict regimen of food deprivation and physical training. This caused his health to become so frail, that he was put on medical supervision for several months after the shoot. However, his efforts didn't go unnoticed: director Francis Ford Coppola was so impressed by Damon's display of method acting, that he offered him the leading role in The Rainmaker (1997). While making Good Will Hunting (1997), after regaining his healthy weight, Damon met Steven Spielberg (who was then casting Saving Private Ryan (1998)). Spielberg told Damon that he had loved his performance in "Courage Under Fire" and had wanted to hire him to play Private Ryan, but was afraid that Damon was too skinny. Once Spielberg saw Damon at his normal weight, he hired him for Ryan.
Matt Damon not only went on an extreme diet, he would also run twelve miles a day, drinking four to six pots of coffee to muster up the energy. His extreme dieting went to the point where he had to had to wash his mouth every time his girlfriend kissed him, because he could taste what she had been eating. Director Edward Zwick got so scared by Damon's emaciated appearance that he ordered the actor to start eating again, but Damon refused. Unfortunately for him, as he was not an established star at the time, he had to do all of this under his own steam, without the help of a nutritionist. After filming was done, Damon was diagnosed with deregulated blood sugar, which required medication. It would take Damon a good two years to get his body back to normal.
To prepare for his part in the film, Denzel Washington met with two combat veterans from the Gulf War, to ask about their experiences there, and any particular memories that had stuck with them since the war.
The unit portrayed in the movie, commanded by Lieutenant Colonel Serling, is the 2nd Armored Cavalry Regiment (2nd ACR). The Regiment was comprised of heavy tanks (M1A1) and fighting vehicles (Bradly FV M3). The unit as such no longer exists. It is now known as the 2nd Cavalry Regiment (Stryker) which fights as an infantry (non-tanks) unit.
The patch on Sterling's shoulder is referring to the U.S. Army 2nd Cavalry. The motto in french "toujours prêt" means "Always Ready" and the fleur-de-lis is related to the fact that they fought in France during both World Wars.
Denzel Washington visited with B 1-12 CAV at Fort Hood, to prepare for his role of Lieutenant Colonel Nate Serling. The dip he puts in, while giving his OPORD in the opening sequence, is a tribute to the time he spent with B 1-12.
In the scene where Sterling is packing to begin his trip to investigate the Medal of Honor, there is a picture on the bedroom wall of the Watts Towers in Los Angels, CA. These towers were also the stage for the final climactic scene of another Denzel Washington movie, Ricochet (1991).
The trivia item below may give away important plot points.
When Lieutenant Colonel Serling meets Sergeant Monfriez for the first time, Monfriez is chastising a trainee soldier for leaving his comrades behind. It's ironic that a major aspect of the plot involves Monfriez doing just that to Captain Walden.